A will doesn’t do you much good in the grand scheme of things if it is not a valid will. To be valid, there are certain legal requirements for a will. First and foremost, you must be of sound mind when you create the will. Next, you must date and sign the will, and the will must be signed by two to three other witnesses (depending on your state) – and the witnesses must watch you sign the will, even if they don’t read the contents of it. Finally, you must declare in the will that it is, in fact, a will. Also, it doesn’t hurt (though it’s not absolutely required) to have your signature or your witnesses’ signatures notarized.
Also, you don’t need to file your will with a court to make it legal. Just make sure that it is located in a safe place where your executor can find it.